Ajax success function shows "1" on the top left corner of blank page instead of refreshing the div

I am developing a yii2 application. I select data from the Bootstrap modal popup and submit to a controller action where I have an insert query. After I submit the data from modal popupthe data is submitted it shows a white page with "1" on the top left corner of the page instead of only closing the popup and refreshing the div but as I checked in the database data is inserted.